Unexpected UI Lag When Using SwiftUI with Combine on iOS 17
I'm experimenting with Hey everyone, I'm running into an issue that's driving me crazy... I'm experiencing significant UI lag in my SwiftUI application when using Combine to update my view model... The app is built with SwiftUI and targets iOS 17. The issue arises when a substantial amount of data is fetched from an API and processed on the main thread, leading to unresponsive UI during the updates. I tried using `DispatchQueue.global().async` to fetch and process the data off the main thread, but I still see the lag when the UI is trying to reflect the changes. Here's a simplified version of my view model: ```swift import Combine import SwiftUI class MyViewModel: ObservableObject { @Published var items: [String] = [] private var cancellables = Set<AnyCancellable>() func fetchData() { // Simulating an API call DispatchQueue.global().async { [weak self] in let data = (0..<1000).map { "Item \($0)" } // Simulated data DispatchQueue.main.async { self?.items = data // Assigning to published property } } } } ``` And here's how I'm using the view model in my SwiftUI view: ```swift struct ContentView: View { @StateObject private var viewModel = MyViewModel() var body: some View { List(viewModel.items, id: \.self) { item in Text(item) } .onAppear { viewModel.fetchData() } } } ``` Despite using async to fetch data, the UI still lags when the `items` array is assigned a large number of entries. I also considered using `withAnimation` when updating the `items`, but it didn’t resolve the issue. My goal is to maintain a smooth UI experience while updating the list with a large dataset. What are some best practices or design patterns I could use to avoid this lag? Any specific optimizations for handling large datasets in SwiftUI? Any help would be greatly appreciated! What am I doing wrong? Am I missing something obvious?